Before replacing the galvanized with PVC there were only leaks not drainage problems, but now the drains will do nothing. The sink clogs up into the tub and the sink pipe is lower then the tub line it connects at an elbow and cannot get the snake past that elbow. Could there be a venting problem. We even tried acid to relieve any blockages and that is not working. HELP

First off stop with the acid completely. Add some water every once in awhile to flush the acid out. Could just be a coincidence, sounds like your branch drain is clogged after the tub. Rod down by removing the over flow plate, rod with a 1/4" snake or rotary auger on a drill

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We even tried acid to relieve any blockages and that is not working.

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I can not advise against using muratic acid, or any acid, in a enclosed area such as a rest room strongly enough. As a young boy I would take limed up toilet bowls out in the alley behind the shop and boil the lime out of them. Over half a century later my lungs still carry the scar tissue that the acid fumes caused. A few years ago I lost a good friend when he used a commercial drain cleaner containing sulfuric acid in a unvented bathroom. Acid IS NOT A GOOD IDEA to use to clear mineral buildup. Take it from one who's paid the price.
You have a blockage downstream from the tub. Snake from the tub waste and overflow, (see image). You will run into the trap bend about 18 inched down but once past that you only have to put out about 15 more
Feet. Good luck, Tom